March 1, 1517.
From our cloister in Wittenberg. Martin Luther, of the Augustinian Order. To John Lange
I am at present reading our Erasmus, but my heart recoils more and more from him. But one thing I admire is, that he constantly and learnedly accuses not only the monks, but the priests, of a lazy, deep-rooted ignorance.
Only, I fear he does not spread Christ and God’s grace sufficiently abroad, of which he knows very little. The human is to him of more importance than the divine.
Although unwilling to judge him, I warn you not to read blindly what he writes. For we live in perilous times, and every one who is a good Hebrew and Greek scholar is not a true Christian; even Dr. Hieronymus, with his five languages, cannot approach Augustine with his one tongue, although Erasmus views all this from a different standpoint. Those who ascribe something to man’s freedom of will regard those things differently from those who know only God’s free grace.
Source: Luther's Letters
I found this letter interesting for a few reasons. First, the date of its composition was March 1, 1517, months before the posting of the 95 Theses. Much debate surrounds when exactly Luther had his "evangelical breakthrough". Many scholars find Luther's understanding of Justification growing, and coming to fruition sometime after the posting of the 95 Theses. In this letter, it's obvious Luther was well on his to his understanding of justification, for "Those who ascribe something to man’s freedom of will regard those things differently from those who know only God’s free grace."
Second, the letter itself is understood best by a comment that Packer and Johnston make in their introduction to Luther's Bondage of the Will:
"Writing to Spalatin in October 1516, Luther had remarked that he considered Augustine the greatest exegetical writer and Jerome a poor second. Erasmus would have reversed the order. Erasmus followed Jerome in interpreting the justification by works against which Paul writes as merely justification by outward ceremonial observance. Luther, believing that any kind of effort or contribution man may attempt to make towards his own salvation is works-righteousness, and therefore under condemnation, preferred the thorough-going exegesis of Augustine, who magnifies the grace of God. If the person is changed, then- and only then- will the good works follow. Such was Luther's position."
Source: Martin Luther, The Bondage of the Will [(Translated by J.I. Packer and O.R.Johnston),Grand Rapids: Revell, 1957, p.25].
One can see from this letter and background the two usual interpretations of Paul's letter to the Romans at work in the theology of Luther and Erasmus: Luther and the Protestants, affirming man's total helplessness and need of grace; Erasmus and Rome, interpreting Paul only to mean "ceremonial law", and assuming mankind's ablity to contribute to one's own eventual (or possible) salvation.
In December 1525, Luther makes this point in The Bondage of The Will, even questioning the salvation of Jerome when discussing what Paul means by "law":
"Paul's meaning is commonly escaped and avoided by saying that what he calls 'works of the law' are ceremonial works, which since the death of Christ are death-dealing. I reply: This is the error of ignorant Jerome, which, for all Augustine's strenuous resistance, spread throughout the world when God withdrew, and Satan prevailed, and has continued to this day; with the result that it has been impossible to understand Paul, and the knowledge of Christ has been inevitably obscured. Had there been no other error in the church, this one was sufficiently potent and destructive to wreck the gospel. Unless extraordinary grace has interposed, Jerome deserved hell rather than heaven for it—so far am I from having the audacity to canonise him and call him a saint! It is not true that Paul is here speaking only of ceremonial works; else, how will his argument to prove that all are unrighteous and need grace, stand good? For one could then say: Granted, we are not justified by ceremonial works; but a man can be justified by the moral works of the Decalogue. So your syllogism [Erasmus] has not proved that grace is necessary to all men. And how profitable, in that case, grace would be, delivering us merely from ceremonial
works, which are the easiest works of all, and can be screwed out of us by plain fear or self-love!Moreover, it is erroneous to say that ceremonial works are deadly and unlawful since the death of Christ. Paul never said that. What he says is that they do not justify, or in any way help man to free himself from ungodliness in God's sight. It is fully compatible with this that one can do them without doing anything unlawful. Eating and drinking are works which do not justify or commend us to God, yet he who eats and drinks does not therefore do something unlawful."
Source: Martin Luther, The Bondage of the Will [(Translated by J.I. Packer and O.R.Johnston),Grand Rapids: Revell, 1957, p.284].